Polyether ether ketone(PEEK)was widely used because of its excellent comprehensive performance,which was often subject to thermal mechanical coupling.TGA testing showed that decomposition begins at 520 ℃ in air in which first carbonization was followed by oxidation combustion.The relaxation curves under different strain deformations showed that the larger the initial strain,the higher the stress level,and the more significant the decrease in stress during relaxation.The higher the temperature,the lower the stress level but the greater the relaxation stress amplitude.At 5％loading strain,the relaxation behavior slowed down with loading speed.At very low loading rates,the stress level was low since the material could respond in time while the stress relaxation amplitude was large.When loading at medium to high speeds,the response stress decreases with the increase of loading speed while the amplitude of relaxation stress decreases.Nonlinear equation fitting reveals that relaxation under loading can be divided into elastic forced relaxation,long plasticization relaxation of molecular chain and short one.Under a certain stress,the larger the load,the higher the strain level in creep,and the more obvious the strain growth.The higher the temperature,the greater the creep amplitude.Nonlinear fitting analysis showed that creep under loading could be divided into elastic forced creep,first-order plastic creep and second-order one.
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